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<div class="titlepage"><div><div><h2 class="title" style="clear: both">
<a name="intrusive.equal_range_stability"></a><a class="link" href="equal_range_stability.html" title="Stability and insertion with hint in ordered associative containers with equivalent keys">Stability and insertion
    with hint in ordered associative containers with equivalent keys</a>
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<p>
      <span class="bold"><strong>Boost.Intrusive</strong></span> ordered associative containers
      with equivalent keys offer stability guarantees, following <a href="http://open-std.org/jtc1/sc22/wg21/docs/lwg-defects.html#233" target="_top">C++
      standard library's defect #233 resolution</a>, explained in document <a href="http://www.open-std.org/jtc1/sc22/wg21/docs/papers/2005/n1780.html" target="_top">Comments
      on LWG issue 233: Insertion hints in associative containers</a>. This means
      that:
    </p>
<div class="itemizedlist"><ul class="itemizedlist" style="list-style-type: disc; ">
<li class="listitem">
          A <span class="emphasis"><em>Insert without hint</em></span> member function always insert
          at the upper bound of an equal range.
        </li>
<li class="listitem">
          A <span class="emphasis"><em>Insert with hint</em></span> member function inserts the new
          value <span class="bold"><strong>before the hint</strong></span> if hint's and new
          node's keys are equivalent.
        </li>
<li class="listitem">
          Implements Andrew Koenig <span class="emphasis"><em>as close as possible to hint</em></span>
          proposal. A new element is always be inserted as close to the hint as possible.
          So, for example, if there is a subsequence of equivalent values, <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()</span></code> as the hint means that the new element
          should be inserted before the subsequence even if <code class="computeroutput"><span class="identifier">a</span><span class="special">.</span><span class="identifier">begin</span><span class="special">()</span></code> is far away. This allows code to always
          append (or prepend) an equal range with something as simple as: <code class="computeroutput"><span class="identifier">m</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span><span class="identifier">m</span><span class="special">.</span><span class="identifier">end</span><span class="special">(),</span> <span class="identifier">new_node</span><span class="special">);</span></code>
          or <code class="computeroutput"><span class="identifier">m</span><span class="special">.</span><span class="identifier">insert</span><span class="special">(</span><span class="identifier">m</span><span class="special">.</span><span class="identifier">begin</span><span class="special">(),</span> <span class="identifier">new_node</span><span class="special">);</span></code>
        </li>
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<td align="right"><div class="copyright-footer">Copyright © 2005 Olaf Krzikalla<br>Copyright © 2006-2015 Ion Gaztanaga<p>
        Distributed under the Boost Software License, Version 1.0. (See accompanying
        file LICENSE_1_0.txt or copy at <a href="http://www.boost.org/LICENSE_1_0.txt" target="_top">http://www.boost.org/LICENSE_1_0.txt</a>)
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